We propose to establish a Mass Spectrometry Resource to support and develop the technique of gas chromatography/mass spectrometry for applications in basic and clinical biochemistry. The Resource will concentrate on three objectives: 1) The support of research requiring mass spectrometry that extends the methodology and areas of application of this technique. The Resource will concentrate its support and development efforts on research by users that requires either great sensitivity in analysis, characterization of complex mixtures, or the use of stable isotopes for tracer analysis. Research requiring very sensitive analyses includes work with prostaglandins, catecholamines, inositols in nerve cells, tricyclic antidepressants, and plasticizers in heart tissue. Characterization of complex mixtures will be required for investigation of inborn errors of metabolism, the metabolism of vitamin D, and various drug assays. Stable isotope tracers will be used to study ketohypoglycemia in children, abnormalities of alanine metabolism found in congenital cyanotic heart disease and muscular dystrophy, and pathways for amino acid synthesis in plants. 2) The development of chemical methods for mass spectrometry, including synthesis of stable isotope labelled compounds for internal standards and stable tracer analysis, synthesis of new derivatives with favorable GC characteristics or fragmentation patterns, the use of high resolution capillary columns, and chemical ionization mass spectrometry. 3) The development of computer programs and digital circuits that extend the basic performance of the mass spectrometer in sensitivity and speed, and provide convenient, inexpensive, and efficient methods of data acquisition and processing, including routine identification of mass spectra. Quadrupole mass spectrometer technology will be developed, including the use of a medium resolution instrument for atomic composition analysis.